Cold Email Deliverability: How to Keep Instantly Campaigns Out of Spam
The technical and practical factors that decide whether your cold emails reach the inbox, and how to set them up in Instantly.
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Cold email deliverability comes down to whether mailbox providers trust your sending. That trust is built from correct authentication, a healthy domain and inbox reputation, sensible sending volume, clean lists with low bounces, low spam complaints and relevant, simple emails. Instantly gives you the tools to manage most of this, but the decisions are yours. Get the foundations right and most campaigns reach the inbox. Skip them and even good emails land in spam.
1. Use separate sending domains
Send cold outreach from domains related to, but separate from, your main business domain. This protects the domain your normal business email depends on. Redirect sending domains to your main website, and spread inboxes across several domains so problems on one do not stop everything.
2. Authenticate everything
- SPF tells receiving servers which services may send email for your domain.
- DKIM adds a cryptographic signature proving the email was not altered and came from your domain.
- DMARC tells receivers what to do with emails that fail SPF or DKIM, and gives you reporting.
Major providers including Google and Yahoo introduced stricter sender requirements in 2024, including authentication, keeping spam complaint rates low, and easy unsubscribes for bulk senders. Even if your volume is below bulk thresholds, meeting these standards is the safest approach. A custom tracking domain is also recommended if you track links.
3. Warm up and send gradually
New inboxes need warmup before campaigns and modest daily limits afterwards. Spread volume across many inboxes, add random delays between sends, and schedule during business hours. See Instantly email warmup.
4. Keep your list clean
Bounces are one of the fastest ways to damage reputation. Verify emails before importing, remove role addresses where appropriate, avoid catch-all addresses in large numbers, and remove bounced contacts immediately. Keep bounce rates as low as possible.
5. Target tightly to avoid complaints
Spam complaints come from people who feel the email is irrelevant. Precise targeting, a clear reason for contacting someone and an easy opt-out keep complaints down. Sending to people with no plausible interest in your offer is the biggest deliverability risk of all.
6. Write emails that look like real email
- Plain text, short, and conversational.
- Few or no links in the first email, and no attachments.
- No heavy images, HTML templates or spammy phrases.
- Personalised where it is genuinely relevant.
- Use spintax and variation thoughtfully so every email is not identical.
Our guide to writing Instantly sequences covers copy in more detail.
7. Be careful with tracking
Open tracking adds a tracking pixel and click tracking rewrites links, both of which can affect deliverability. Many experienced senders turn off open tracking for cold campaigns and measure replies instead. If you track clicks, use a custom tracking domain.
8. Monitor and react
Watch bounce rates, reply rates, inbox health in Instantly and placement test results. If performance drops, reduce volume, pause affected inboxes, check DNS records and list quality, and resume gradually.
9. Stay compliant
Cold email is legal in many places for B2B outreach when done properly, but rules vary by country. Identify yourself clearly, include a working opt-out, honour it promptly, and follow data protection rules in the regions you target. When in doubt, take local advice.
Want outbound that reaches the inbox?
We set up domains, DNS, warmup, list verification and campaign settings in Instantly, then monitor deliverability as campaigns run. See our AI Automation Systems service, our Instantly setup guide, or get in touch.